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CURRENT UNDERWATER WELDING TECHNOLOGIES

This report involves both original generation of experimental data and the integration and evaluation of previously generated information. The preliminary sections allow the reader to evaluate the functional importance of this research and understand the relationships between these experimental investigations and the rest of the "world of underwater welding." The opening section reports the overall development that has taken place in underwater welding technologies. This material gives the reader an introductory familiarity with the basic welding techniques and capabilities in underwater situations. Experimental investigations of underwater welding have produced data that has not been adequately collected, sorted, and presented in a unified manner. A section of this report attempts this compilation of previous results. The general principles and conceptual framework of welding metallurgy and microstructure are presented. Basic air welding results and phenomena are explained and modified or interpreted to apply to the peculiar conditions of underwater welding. The objective of the research is to generate the experimental data needed as a basis for recommending the procedures that should be employed with a chosen joint design for producing optimum mechanical properties in an underwater welding fabrication situation. Bead on plate welds were produced in both air and water situations and the resulting weld beads are analyzed to document the differences between air and underwater welding. The bulk of the material relates to the analysis and documentation of the information obtained in this comparative study. The type of data produced include: a) Welding current and voltage recordings, b) Welded bead appearance and regularity, c) Geometrical measurements and comparisons, d) Microhardness profiles and comparisions, and e) Microstructural studies of the weld HAZ.